Dipole modulation engineering for the recycling of spent lithium iron phosphate

Abstract

The recycling of spent lithium iron phosphate (S-LFP) is crucial for achieving closed-loop resource utilization in the new energy industry. However, the primary challenges for S-LFP stem from the precise regulation of elemental valence states and the restoration of lithium vacancies. Based on the rocking-chair battery mechanism (Operating mechanism of lithium-ion batteries), LFP undergoes Fe valence state elevation and lithium node vacancies during the repeated cycling, the critical issue undermines its structural integrity. By exploiting the dipole chemistry of dual eutectic solvents (LiI-LiOH) to modulate lattice structure through valence state modulation and site-specific manipulation, this enables efficient repair of S-LFP by addressing Li⁺ deficiency-induced Fe³⁺ reduction to amend valence state, driving lithium back to the lattice nodes, and compensating carbonaceous layers on particle surfaces. Consequentially, repaired LiFePO₄ batteries demonstrate exceptional electrochemical performance, retaining 82.4% of their initial capacity after 1000 cycles at 10 C.